package j2me.util.collections;

import java.util.Hashtable;
import java.util.NoSuchElementException;

/**
 * Hash table based implementation of the <tt>Map</tt> interface. This
 * implementation provides all of the optional map operations, and permits
 * <tt>null</tt> values and the <tt>null</tt> key. (The <tt>HashMap</tt> class
 * is roughly equivalent to <tt>Hashtable</tt>, except that it is unsynchronized
 * and permits nulls.) This class makes no guarantees as to the order of the
 * map; in particular, it does not guarantee that the order will remain constant
 * over time.
 *
 * <p>This implementation provides constant-time performance for the basic
 * operations (<tt>get</tt> and <tt>put</tt>), assuming the hash function
 * disperses the elements properly among the buckets. Iteration over collection
 * views requires time proportional to the "capacity" of the <tt>HashMap</tt>
 * instance (the number of buckets) plus its size (the number of key-value
 * mappings). Thus, it's very important not to set the initial capacity too high
 * (or the load factor too low) if iteration performance is important.
 *
 * <p>An instance of <tt>HashMap</tt> has two parameters that affect its
 * performance: <i>initial capacity</i> and <i>load factor</i>. The
 * <i>capacity</i> is the number of buckets in the hash table, and the initial
 * capacity is simply the capacity at the time the hash table is created. The
 * <i>load factor</i> is a measure of how full the hash table is allowed to get
 * before its capacity is automatically increased. When the number of entries in
 * the hash table exceeds the product of the load factor and the current
 * capacity, the hash table is <i>rehashed</i> (that is, internal data
 * structures are rebuilt) so that the hash table has approximately twice the
 * number of buckets.
 *
 * <p>As a general rule, the default load factor (.75) offers a good tradeoff
 * between time and space costs. Higher values decrease the space overhead but
 * increase the lookup cost (reflected in most of the operations of the
 * <tt>HashMap</tt> class, including <tt>get</tt> and <tt>put</tt>). The
 * expected number of entries in the map and its load factor should be taken
 * into account when setting its initial capacity, so as to minimize the number
 * of rehash operations. If the initial capacity is greater than the maximum
 * number of entries divided by the load factor, no rehash operations will ever
 * occur.
 *
 * <p>If many mappings are to be stored in a <tt>HashMap</tt> instance, creating
 * it with a sufficiently large capacity will allow the mappings to be stored
 * more efficiently than letting it perform automatic rehashing as needed to
 * grow the table.
 *
 * <p><strong>Note that this implementation is not synchronized.</strong> If
 * multiple threads access a hash map concurrently, and at least one of the
 * threads modifies the map structurally, it <i>must</i> be synchronized
 * externally. (A structural modification is any operation that adds or deletes
 * one or more mappings; merely changing the value associated with a key that an
 * instance already contains is not a structural modification.) This is
 * typically accomplished by synchronizing on some object that naturally
 * encapsulates the map.
 *
 * If no such object exists, the map should be "wrapped" using the
 * {@link Collections#synchronizedMap Collections.synchronizedMap} method. This
 * is best done at creation time, to prevent accidental unsynchronized access to
 * the map:
 * <pre>
 *   Map m = Collections.synchronizedMap(new HashMap(...));</pre>
 *
 * <p>The iterators returned by all of this class's "collection view methods"
 * are <i>fail-fast</i>: if the map is structurally modified at any time after
 * the iterator is created, in any way except through the iterator's own
 * <tt>remove</tt> method, the iterator will throw a
 * {@link ConcurrentModificationException}. Thus, in the face of concurrent
 * modification, the iterator fails quickly and cleanly, rather than risking
 * arbitrary, non-deterministic behavior at an undetermined time in the future.
 *
 * <p>Note that the fail-fast behavior of an iterator cannot be guaranteed as it
 * is, generally speaking, impossible to make any hard guarantees in the
 * presence of unsynchronized concurrent modification. Fail-fast iterators throw
 * <tt>ConcurrentModificationException</tt> on a best-effort basis. Therefore,
 * it would be wrong to write a program that depended on this exception for its
 * correctness: <i>the fail-fast behavior of iterators should be used only to
 * detect bugs.</i>
 *
 * <p>This class is a member of the <a
 * href="{@docRoot}/../technotes/guides/collections/index.html"> Java
 * Collections Framework</a>.
 *
 * @param the type of keys maintained by this map
 * @param the type of mapped values
 *
 * @author Doug Lea
 * @author Josh Bloch
 * @author Arthur van Hoff
 * @author Neal Gafter
 * @see Object#hashCode()
 * @see Collection
 * @see Map
 * @see TreeMap
 * @see Hashtable
 * @since 1.2
 */
public class HashMap
        extends AbstractMap
        implements Map, Cloneable {

    /**
     * The default initial capacity - MUST be a power of two.
     */
    static final int DEFAULT_INITIAL_CAPACITY = 16;
    /**
     * The maximum capacity, used if a higher value is implicitly specified by
     * either of the constructors with arguments. MUST be a power of two <=
     * 1<<30.
     */
    static final int MAXIMUM_CAPACITY = 1 << 30;
    /**
     * The load factor used when none specified in constructor.
     */
    static final float DEFAULT_LOAD_FACTOR = 0.75f;
    /**
     * The table, resized as necessary. Length MUST Always be a power of two.
     */
    transient Entry[] table;
    /**
     * The number of key-value mappings contained in this map.
     */
    transient int size;
    /**
     * The next size value at which to resize (capacity * load factor).
     *
     * @serial
     */
    int threshold;
    /**
     * The load factor for the hash table.
     *
     * @serial
     */
    final float loadFactor;
    /**
     * The number of times this HashMap has been structurally modified
     * Structural modifications are those that change the number of mappings in
     * the HashMap or otherwise modify its internal structure (e.g., rehash).
     * This field is used to make iterators on Collection-views of the HashMap
     * fail-fast. (See ConcurrentModificationException).
     */
    transient int modCount;

    /**
     * Constructs an empty <tt>HashMap</tt> with the specified initial capacity
     * and load factor.
     *
     * @param initialCapacity the initial capacity
     * @param loadFactor the load factor
     * @throws IllegalArgumentException if the initial capacity is negative or
     * the load factor is nonpositive
     */
    public HashMap(int initialCapacity, float loadFactor) {
        if (initialCapacity < 0) {
            throw new IllegalArgumentException("Illegal initial capacity: "
                    + initialCapacity);
        }
        if (initialCapacity > MAXIMUM_CAPACITY) {
            initialCapacity = MAXIMUM_CAPACITY;
        }
        if (loadFactor <= 0 || Float.isNaN(loadFactor)) {
            throw new IllegalArgumentException("Illegal load factor: "
                    + loadFactor);
        }

        // Find a power of 2 >= initialCapacity
        int capacity = 1;
        while (capacity < initialCapacity) {
            capacity <<= 1;
        }

        this.loadFactor = loadFactor;
        threshold = (int) (capacity * loadFactor);
        table = new Entry[capacity];
        init();
    }

    /**
     * Constructs an empty <tt>HashMap</tt> with the specified initial capacity
     * and the default load factor (0.75).
     *
     * @param initialCapacity the initial capacity.
     * @throws IllegalArgumentException if the initial capacity is negative.
     */
    public HashMap(int initialCapacity) {
        this(initialCapacity, DEFAULT_LOAD_FACTOR);
    }

    /**
     * Constructs an empty <tt>HashMap</tt> with the default initial capacity
     * (16) and the default load factor (0.75).
     */
    public HashMap() {
        this.loadFactor = DEFAULT_LOAD_FACTOR;
        threshold = (int) (DEFAULT_INITIAL_CAPACITY * DEFAULT_LOAD_FACTOR);
        table = new Entry[DEFAULT_INITIAL_CAPACITY];
        init();
    }

    /**
     * Constructs a new <tt>HashMap</tt> with the same mappings as the specified
     * <tt>Map</tt>. The <tt>HashMap</tt> is created with default load factor
     * (0.75) and an initial capacity sufficient to hold the mappings in the
     * specified <tt>Map</tt>.
     *
     * @param m the map whose mappings are to be placed in this map
     * @throws NullPointerException if the specified map is null
     */
    public HashMap(Map m) {
        this(Math.max((int) (m.size() / DEFAULT_LOAD_FACTOR) + 1,
                DEFAULT_INITIAL_CAPACITY), DEFAULT_LOAD_FACTOR);
        putAllForCreate(m);
    }

    // internal utilities
    /**
     * Initialization hook for subclasses. This method is called in all
     * constructors and pseudo-constructors (clone, readObject) after HashMap
     * has been initialized but before any entries have been inserted. (In the
     * absence of this method, readObject would require explicit knowledge of
     * subclasses.)
     */
    void init() {
    }

    /**
     * Applies a supplemental hash function to a given hashCode, which defends
     * against poor quality hash functions. This is critical because HashMap
     * uses power-of-two length hash tables, that otherwise encounter collisions
     * for hashCodes that do not differ in lower bits. Note: Null keys always
     * map to hash 0, thus index 0.
     */
    static int hash(int h) {
        // This function ensures that hashCodes that differ only by
        // constant multiples at each bit position have a bounded
        // number of collisions (approximately 8 at default load factor).
        h ^= (h >>> 20) ^ (h >>> 12);
        return h ^ (h >>> 7) ^ (h >>> 4);
    }

    /**
     * Returns index for hash code h.
     */
    static int indexFor(int h, int length) {
        return h & (length - 1);
    }

    /**
     * Returns the number of key-value mappings in this map.
     *
     * @return the number of key-value mappings in this map
     */
    public int size() {
        return size;
    }

    /**
     * Returns <tt>true</tt> if this map contains no key-value mappings.
     *
     * @return <tt>true</tt> if this map contains no key-value mappings
     */
    public boolean isEmpty() {
        return size == 0;
    }

    /**
     * Returns the value to which the specified key is mapped, or {@code null}
     * if this map contains no mapping for the key.
     *
     * <p>More formally, if this map contains a mapping from a key
     * {@code k} to a value {@code v} such that {@code (key==null ? k==null :
     * key.equals(k))}, then this method returns {@code v}; otherwise it returns {@code null}.
     * (There can be at most one such mapping.)
     *
     * <p>A return value of {@code null} does not <i>necessarily</i> indicate
     * that the map contains no mapping for the key; it's also possible that the
     * map explicitly maps the key to {@code null}. The {@link #containsKey containsKey}
     * operation may be used to distinguish these two cases.
     *
     * @see #put(Object, Object)
     */
    public Object get(Object key) {
        if (key == null) {
            return getForNullKey();
        }
        int hash = hash(key.hashCode());
        for (Entry e = table[indexFor(hash, table.length)];
                e != null;
                e = e.next) {
            Object k;
            if (e.hash == hash && ((k = e.key) == key || key.equals(k))) {
                return e.value;
            }
        }
        return null;
    }

    /**
     * Offloaded version of get() to look up null keys. Null keys map to index
     * 0. This null case is split out into separate methods for the sake of
     * performance in the two most commonly used operations (get and put), but
     * incorporated with conditionals in others.
     */
    private Object getForNullKey() {
        for (Entry e = table[0]; e != null; e = e.next) {
            if (e.key == null) {
                return e.value;
            }
        }
        return null;
    }

    /**
     * Returns <tt>true</tt> if this map contains a mapping for the specified
     * key.
     *
     * @param key The key whose presence in this map is to be tested
     * @return <tt>true</tt> if this map contains a mapping for the specified
     * key.
     */
    public boolean containsKey(Object key) {
        return getEntry(key) != null;
    }

    /**
     * Returns the entry associated with the specified key in the HashMap.
     * Returns null if the HashMap contains no mapping for the key.
     */
    final Entry getEntry(Object key) {
        int hash = (key == null) ? 0 : hash(key.hashCode());
        for (Entry e = table[indexFor(hash, table.length)];
                e != null;
                e = e.next) {
            Object k;
            if (e.hash == hash
                    && ((k = e.key) == key || (key != null && key.equals(k)))) {
                return e;
            }
        }
        return null;
    }

    /**
     * Associates the specified value with the specified key in this map. If the
     * map previously contained a mapping for the key, the old value is
     * replaced.
     *
     * @param key key with which the specified value is to be associated
     * @param value value to be associated with the specified key
     * @return the previous value associated with <tt>key</tt>, or <tt>null</tt>
     * if there was no mapping for <tt>key</tt>. (A <tt>null</tt> return can
     * also indicate that the map previously associated <tt>null</tt> with
     * <tt>key</tt>.)
     */
    public Object put(Object key, Object value) {
        if (key == null) {
            return putForNullKey(value);
        }
        int hash = hash(key.hashCode());
        int i = indexFor(hash, table.length);
        for (Entry e = table[i]; e != null; e = e.next) {
            Object k;
            if (e.hash == hash && ((k = e.key) == key || key.equals(k))) {
                Object oldValue = e.value;
                e.value = value;
                e.recordAccess(this);
                return oldValue;
            }
        }

        modCount++;
        addEntry(hash, key, value, i);
        return null;
    }

    /**
     * Offloaded version of put for null keys
     */
    private Object putForNullKey(Object value) {
        for (Entry e = table[0]; e != null; e = e.next) {
            if (e.key == null) {
                Object oldValue = e.value;
                e.value = value;
                e.recordAccess(this);
                return oldValue;
            }
        }
        modCount++;
        addEntry(0, null, value, 0);
        return null;
    }

    /**
     * This method is used instead of put by constructors and pseudoconstructors
     * (clone, readObject). It does not resize the table, check for
     * comodification, etc. It calls createEntry rather than addEntry.
     */
    private void putForCreate(Object key, Object value) {
        int hash = (key == null) ? 0 : hash(key.hashCode());
        int i = indexFor(hash, table.length);

        /**
         * Look for preexisting entry for key. This will never happen for clone
         * or deserialize. It will only happen for construction if the input Map
         * is a sorted map whose ordering is inconsistent w/ equals.
         */
        for (Entry e = table[i]; e != null; e = e.next) {
            Object k;
            if (e.hash == hash
                    && ((k = e.key) == key || (key != null && key.equals(k)))) {
                e.value = value;
                return;
            }
        }

        createEntry(hash, key, value, i);
    }

    private void putAllForCreate(Map m) {

        for (Iterator i = m.entrySet().iterator(); i.hasNext();) {
            Entry e = (Entry) i.next();
            putForCreate(e.getKey(), e.getValue());
        }
    }

    /**
     * Rehashes the contents of this map into a new array with a larger
     * capacity. This method is called automatically when the number of keys in
     * this map reaches its threshold.
     *
     * If current capacity is MAXIMUM_CAPACITY, this method does not resize the
     * map, but sets threshold to Integer.MAX_VALUE. This has the effect of
     * preventing future calls.
     *
     * @param newCapacity the new capacity, MUST be a power of two; must be
     * greater than current capacity unless current capacity is MAXIMUM_CAPACITY
     * (in which case value is irrelevant).
     */
    void resize(int newCapacity) {
        Entry[] oldTable = table;
        int oldCapacity = oldTable.length;
        if (oldCapacity == MAXIMUM_CAPACITY) {
            threshold = Integer.MAX_VALUE;
            return;
        }

        Entry[] newTable = new Entry[newCapacity];
        transfer(newTable);
        table = newTable;
        threshold = (int) (newCapacity * loadFactor);
    }

    /**
     * Transfers all entries from current table to newTable.
     */
    void transfer(Entry[] newTable) {
        Entry[] src = table;
        int newCapacity = newTable.length;
        for (int j = 0; j < src.length; j++) {
            Entry e = src[j];
            if (e != null) {
                src[j] = null;
                do {
                    Entry next = e.next;
                    int i = indexFor(e.hash, newCapacity);
                    e.next = newTable[i];
                    newTable[i] = e;
                    e = next;
                } while (e != null);
            }
        }
    }

    /**
     * Copies all of the mappings from the specified map to this map. These
     * mappings will replace any mappings that this map had for any of the keys
     * currently in the specified map.
     *
     * @param m mappings to be stored in this map
     * @throws NullPointerException if the specified map is null
     */
    public void putAll(Map m) {
        int numKeysToBeAdded = m.size();
        if (numKeysToBeAdded == 0) {
            return;
        }

        /*
         * Expand the map if the map if the number of mappings to be added is
         * greater than or equal to threshold. This is conservative; the obvious
         * condition is (m.size() + size) >= threshold, but this condition could
         * result in a map with twice the appropriate capacity, if the keys to
         * be added overlap with the keys already in this map. By using the
         * conservative calculation, we subject ourself to at most one extra
         * resize.
         */
        if (numKeysToBeAdded > threshold) {
            int targetCapacity = (int) (numKeysToBeAdded / loadFactor + 1);
            if (targetCapacity > MAXIMUM_CAPACITY) {
                targetCapacity = MAXIMUM_CAPACITY;
            }
            int newCapacity = table.length;
            while (newCapacity < targetCapacity) {
                newCapacity <<= 1;
            }
            if (newCapacity > table.length) {
                resize(newCapacity);
            }
        }

        for (Iterator i = m.entrySet().iterator(); i.hasNext();) {
            Entry e = (Entry) i.next();
            put(e.getKey(), e.getValue());
        }
    }

    /**
     * Removes the mapping for the specified key from this map if present.
     *
     * @param key key whose mapping is to be removed from the map
     * @return the previous value associated with <tt>key</tt>, or <tt>null</tt>
     * if there was no mapping for <tt>key</tt>. (A <tt>null</tt> return can
     * also indicate that the map previously associated <tt>null</tt> with
     * <tt>key</tt>.)
     */
    public Object remove(Object key) {
        Entry e = removeEntryForKey(key);
        return (e == null ? null : e.value);
    }

    /**
     * Removes and returns the entry associated with the specified key in the
     * HashMap. Returns null if the HashMap contains no mapping for this key.
     */
    final Entry removeEntryForKey(Object key) {
        int hash = (key == null) ? 0 : hash(key.hashCode());
        int i = indexFor(hash, table.length);
        Entry prev = table[i];
        Entry e = prev;

        while (e != null) {
            Entry next = e.next;
            Object k;
            if (e.hash == hash
                    && ((k = e.key) == key || (key != null && key.equals(k)))) {
                modCount++;
                size--;
                if (prev == e) {
                    table[i] = next;
                } else {
                    prev.next = next;
                }
                e.recordRemoval(this);
                return e;
            }
            prev = e;
            e = next;
        }

        return e;
    }

    /**
     * Special version of remove for EntrySet.
     */
    final Entry removeMapping(Object o) {
        if (!(o instanceof Map.Entry)) {
            return null;
        }

        Map.Entry entry = (Map.Entry) o;
        Object key = entry.getKey();
        int hash = (key == null) ? 0 : hash(key.hashCode());
        int i = indexFor(hash, table.length);
        Entry prev = table[i];
        Entry e = prev;

        while (e != null) {
            Entry next = e.next;
            if (e.hash == hash && e.equals(entry)) {
                modCount++;
                size--;
                if (prev == e) {
                    table[i] = next;
                } else {
                    prev.next = next;
                }
                e.recordRemoval(this);
                return e;
            }
            prev = e;
            e = next;
        }

        return e;
    }

    /**
     * Removes all of the mappings from this map. The map will be empty after
     * this call returns.
     */
    public void clear() {
        modCount++;
        Entry[] tab = table;
        for (int i = 0; i < tab.length; i++) {
            tab[i] = null;
        }
        size = 0;
    }

    /**
     * Returns <tt>true</tt> if this map maps one or more keys to the specified
     * value.
     *
     * @param value value whose presence in this map is to be tested
     * @return <tt>true</tt> if this map maps one or more keys to the specified
     * value
     */
    public boolean containsValue(Object value) {
        if (value == null) {
            return containsNullValue();
        }

        Entry[] tab = table;
        for (int i = 0; i < tab.length; i++) {
            for (Entry e = tab[i]; e != null; e = e.next) {
                if (value.equals(e.value)) {
                    return true;
                }
            }
        }
        return false;
    }

    /**
     * Special-case code for containsValue with null argument
     */
    private boolean containsNullValue() {
        Entry[] tab = table;
        for (int i = 0; i < tab.length; i++) {
            for (Entry e = tab[i]; e != null; e = e.next) {
                if (e.value == null) {
                    return true;
                }
            }
        }
        return false;
    }

    /**
     * Returns a shallow copy of this <tt>HashMap</tt> instance: the keys and
     * values themselves are not cloned.
     *
     * @return a shallow copy of this map
     */
//    public Object clone() {
//        HashMap result = null;
//       
//        try {
//            result = (HashMap) super.clone();
//        } catch (CloneNotSupportedException e) {
//            // assert false;
//        }
//        result.table = new Entry[table.length];
//        result.entrySet = null;
//        result.modCount = 0;
//        result.size = 0;
//        result.init();
//        result.putAllForCreate(this);
//
//        return result;
//    }
    static class Entry implements Map.Entry {

        final Object key;
        Object value;
        Entry next;
        final int hash;

        /**
         * Creates new entry.
         */
        Entry(int h, Object k, Object v, Entry n) {
            value = v;
            next = n;
            key = k;
            hash = h;
        }

        public final Object getKey() {
            return key;
        }

        public final Object getValue() {
            return value;
        }

        public final Object setValue(Object newValue) {
            Object oldValue = value;
            value = newValue;
            return oldValue;
        }

        public final boolean equals(Object o) {
            if (!(o instanceof Map.Entry)) {
                return false;
            }
            Map.Entry e = (Map.Entry) o;
            Object k1 = getKey();
            Object k2 = e.getKey();
            if (k1 == k2 || (k1 != null && k1.equals(k2))) {
                Object v1 = getValue();
                Object v2 = e.getValue();
                if (v1 == v2 || (v1 != null && v1.equals(v2))) {
                    return true;
                }
            }
            return false;
        }

        public final int hashCode() {
            return (key == null ? 0 : key.hashCode())
                    ^ (value == null ? 0 : value.hashCode());
        }

        public final String toString() {
            return getKey() + "=" + getValue();
        }

        /**
         * This method is invoked whenever the value in an entry is overwritten
         * by an invocation of put(k,v) for a key k that's already in the
         * HashMap.
         */
        void recordAccess(HashMap m) {
        }

        /**
         * This method is invoked whenever the entry is removed from the table.
         */
        void recordRemoval(HashMap m) {
        }
    }

    /**
     * Adds a new entry with the specified key, value and hash code to the
     * specified bucket. It is the responsibility of this method to resize the
     * table if appropriate.
     *
     * Subclass overrides this to alter the behavior of put method.
     */
    void addEntry(int hash, Object key, Object value, int bucketIndex) {
        Entry e = table[bucketIndex];
        table[bucketIndex] = new Entry(hash, key, value, e);
        if (size++ >= threshold) {
            resize(2 * table.length);
        }
    }

    /**
     * Like addEntry except that this version is used when creating entries as
     * part of Map construction or "pseudo-construction" (cloning,
     * deserialization). This version needn't worry about resizing the table.
     *
     * Subclass overrides this to alter the behavior of HashMap(Map), clone, and
     * readObject.
     */
    void createEntry(int hash, Object key, Object value, int bucketIndex) {
        Entry e = table[bucketIndex];
        table[bucketIndex] = new Entry(hash, key, value, e);
        size++;
    }

    private abstract class HashIterator implements Iterator {

        Entry next;        // next entry to return
        int expectedModCount;   // For fast-fail
        int index;              // current slot
        Entry current;     // current entry

        HashIterator() {
            expectedModCount = modCount;
            if (size > 0) { // advance to first entry
                Entry[] t = table;
                while (index < t.length && (next = t[index++]) == null)
                    ;
            }
        }

        public final boolean hasNext() {
            return next != null;
        }

        final Entry nextEntry() {
            if (modCount != expectedModCount) {
                throw new ConcurrentModificationException();
            }
            Entry e = next;
            if (e == null) {
                throw new NoSuchElementException();
            }

            if ((next = e.next) == null) {
                Entry[] t = table;
                while (index < t.length && (next = t[index++]) == null)
                    ;
            }
            current = e;
            return e;
        }

        public void remove() {
            if (current == null) {
                throw new IllegalStateException();
            }
            if (modCount != expectedModCount) {
                throw new ConcurrentModificationException();
            }
            Object k = current.key;
            current = null;
            HashMap.this.removeEntryForKey(k);
            expectedModCount = modCount;
        }
    }

    private final class ValueIterator extends HashIterator {

        public Object next() {
            return nextEntry().value;
        }
    }

    private final class KeyIterator extends HashIterator {

        public Object next() {
            return nextEntry().getKey();
        }
    }

    private final class EntryIterator extends HashIterator {

        public Object next() {
            return nextEntry();
        }
    }

    // Subclass overrides these to alter behavior of views' iterator() method
    Iterator newKeyIterator() {
        return new KeyIterator();
    }

    Iterator newValueIterator() {
        return new ValueIterator();
    }

    Iterator newEntryIterator() {
        return new EntryIterator();
    }
    // Views
    private transient Set entrySet = null;

    /**
     * Returns a {@link Set} view of the keys contained in this map. The set is
     * backed by the map, so changes to the map are reflected in the set, and
     * vice-versa. If the map is modified while an iteration over the set is in
     * progress (except through the iterator's own <tt>remove</tt> operation),
     * the results of the iteration are undefined. The set supports element
     * removal, which removes the corresponding mapping from the map, via the
     * <tt>Iterator.remove</tt>, <tt>Set.remove</tt>, <tt>removeAll</tt>,
     * <tt>retainAll</tt>, and <tt>clear</tt> operations. It does not support
     * the <tt>add</tt> or <tt>addAll</tt> operations.
     */
    public Set keySet() {
        Set ks = keySet;
        return (ks != null ? ks : (keySet = new KeySet()));
    }

    private final class KeySet extends AbstractSet {

        public Iterator iterator() {
            return newKeyIterator();
        }

        public int size() {
            return size;
        }

        public boolean contains(Object o) {
            return containsKey(o);
        }

        public boolean remove(Object o) {
            return HashMap.this.removeEntryForKey(o) != null;
        }

        public void clear() {
            HashMap.this.clear();
        }
    }

    /**
     * Returns a {@link Collection} view of the values contained in this map.
     * The collection is backed by the map, so changes to the map are reflected
     * in the collection, and vice-versa. If the map is modified while an
     * iteration over the collection is in progress (except through the
     * iterator's own <tt>remove</tt> operation), the results of the iteration
     * are undefined. The collection supports element removal, which removes the
     * corresponding mapping from the map, via the <tt>Iterator.remove</tt>,
     * <tt>Collection.remove</tt>, <tt>removeAll</tt>, <tt>retainAll</tt> and
     * <tt>clear</tt> operations. It does not support the <tt>add</tt> or
     * <tt>addAll</tt> operations.
     */
    public Collection values() {
        Collection vs = values;
        return (vs != null ? vs : (values = new Values()));
    }

    private final class Values extends AbstractCollection {

        public Iterator iterator() {
            return newValueIterator();
        }

        public int size() {
            return size;
        }

        public boolean contains(Object o) {
            return containsValue(o);
        }

        public void clear() {
            HashMap.this.clear();
        }
    }

    /**
     * Returns a {@link Set} view of the mappings contained in this map. The set
     * is backed by the map, so changes to the map are reflected in the set, and
     * vice-versa. If the map is modified while an iteration over the set is in
     * progress (except through the iterator's own <tt>remove</tt> operation, or
     * through the <tt>setValue</tt> operation on a map entry returned by the
     * iterator) the results of the iteration are undefined. The set supports
     * element removal, which removes the corresponding mapping from the map,
     * via the <tt>Iterator.remove</tt>, <tt>Set.remove</tt>,
     * <tt>removeAll</tt>, <tt>retainAll</tt> and <tt>clear</tt> operations. It
     * does not support the <tt>add</tt> or <tt>addAll</tt> operations.
     *
     * @return a set view of the mappings contained in this map
     */
    public Set entrySet() {
        return entrySet0();
    }

    private Set entrySet0() {
        Set es = entrySet;
        return es != null ? es : (entrySet = new EntrySet());
    }

    private final class EntrySet extends AbstractSet {

        public Iterator iterator() {
            return newEntryIterator();
        }

        public boolean contains(Object o) {
            if (!(o instanceof Map.Entry)) {
                return false;
            }
            Map.Entry e = (Map.Entry) o;
            Entry candidate = getEntry(e.getKey());
            return candidate != null && candidate.equals(e);
        }

        public boolean remove(Object o) {
            return removeMapping(o) != null;
        }

        public int size() {
            return size;
        }

        public void clear() {
            HashMap.this.clear();
        }
    }
    /**
     * Save the state of the <tt>HashMap</tt> instance to a stream (i.e.,
     * serialize it).
     *
     * @serialData The <i>capacity</i> of the HashMap (the length of the bucket
     * array) is emitted (int), followed by the <i>size</i> (an int, the number
     * of key-value mappings), followed by the key (Object) and value (Object)
     * for each key-value mapping. The key-value mappings are emitted in no
     * particular order.
     */
//    private void writeObject(java.io.ObjectOutputStream s)
//            throws IOException {
//        Iterator i =
//                (size > 0) ? entrySet0().iterator() : null;
//
//        // Write out the threshold, loadfactor, and any hidden stuff
//        s.defaultWriteObject();
//
//        // Write out number of buckets
//        s.writeInt(table.length);
//
//        // Write out size (number of Mappings)
//        s.writeInt(size);
//
//        // Write out keys and values (alternating)
//        if (i != null) {
//            while (i.hasNext()) {
//                Map.Entry e = i.next();
//                s.writeObject(e.getKey());
//                s.writeObject(e.getValue());
//            }
//        }
//    }
    private static final long serialVersionUID = 362498820763181265L;

    /**
     * Reconstitute the <tt>HashMap</tt> instance from a stream (i.e.,
     * deserialize it).
     */
//    private void readObject(java.io.ObjectInputStream s)
//            throws IOException, ClassNotFoundException {
//        // Read in the threshold, loadfactor, and any hidden stuff
//        s.defaultReadObject();
//
//        // Read in number of buckets and allocate the bucket array;
//        int numBuckets = s.readInt();
//        table = new Entry[numBuckets];
//
//        init();  // Give subclass a chance to do its thing.
//
//        // Read in size (number of Mappings)
//        int size = s.readInt();
//
//        // Read the keys and values, and put the mappings in the HashMap
//        for (int i = 0; i < size; i++) {
//            Object key = (K) s.readObject();
//            Object value = (V) s.readObject();
//            putForCreate(key, value);
//        }
//    }
    // These methods are used when serializing HashSets
    int capacity() {
        return table.length;
    }

    float loadFactor() {
        return loadFactor;
    }
}
